The present invention relates to the desulfuration of liquid metals at an elevated temperature by means of a solid electrolyte traversed by a direct current.
During extensive research, the inventors have shown that it is possible to lower the sulfur content in a liquid metal, especially steel, by passing a direct current through a partition formed by a solid electrolyte in contact on both sides with the liquid metal in which the metal to be refined is connected to the negative pole of a direct current supply by means of an electrode. The wall of solid electrolyte is constituted by an oxide of alkaline metals or alkaline earth metals containing a halide of the mentioned metals, especially a halide of calcium and more specifically a fluoride or a chloride of this metal such to assure a good cationic conductivity of the electrolyte by an ion capable to react with the sulfur, for instance the cation Ca.sup.+.sup.+. The oxide constituting the partition wall is preferably lime or a mixture of lime and magnesia in proportions approximately equal to those of dolomite.
During passage of the direct current through the assembly, a transfer of cations through the wall is obtained and a reaction of the cation with the sulfur to result in sulfide which forms a layer adherent to the wall. After proceeding with the electrolysis for a certain time, the sulfur initially contained in the metal bath will be fixed to the wall.
This technique developed in the laboratory could, however, not be carried out on an industrial scale in which the metal to be treated is in the order of 10 tons or more of liquid steel.